Retarder films, sometimes also referred to as retarder plates, are known. A retarder film is constructed such that when normally incident unpolarized light passes through the film, one linear polarization state is delayed or “retarded” relative to an orthogonal linear polarization state. Light of the delayed polarization state is said to be polarized along an in-plane axis of the film referred to as the “slow axis”, and light of the other polarization state is said to be polarized along an orthogonal in-plane “fast axis”. Retarder films are tailored to provide a desired amount of delay or “retardation”, and the retardation may be measured or specified in terms of a fraction of a design wavelength of light. For example, a quarter-wave retarder causes light polarized along the slow axis to be one-fourth of a wavelength out of phase (and delayed) with respect to light polarized along the fast axis. Likewise, a half-wave retarder causes light polarized along the slow axis to be one-half of a wavelength out of phase (and delayed) with respect to light polarized along the fast axis. In these cases, the referenced “wavelength” may be a wavelength in the middle of the visible spectrum, e.g., 560 nm. Retardation may alternatively be measured in terms of the physical or optical distance that the wavefront of the delayed polarization lags behind the wavefront of the other polarization as light of the two polarization states emerge from the retarder film. (The optical distance is the physical distance multiplied by the applicable refractive index.) For the quarter-wave and half-wave examples just mentioned, the retardations are 120 nm (=560/4) and 280 nm (=560/2), respectively.
Some workers have recently proposed fabricating a micro-retardation array for autostereoscopic display systems by micro-patterning a stretched polymeric material. See e.g. “Fabricating Polymeric Micro-retardation Arrays for Autostereoscopic Display System by CO2 Laser Heat Processing Technology” by Tsai et al. in Proceedings of SPIE 3957 (2000), pp. 142-152. In this work, a CO2 laser is used to heat a stretched birefringent polymeric material in a stripe-wise pattern to release internal stress and erase the retardation of the treated area. The workers report inner bubbles under some processing conditions and a change in surface profile to a ruggedly grooved surface.